Matchmaking: Level 30's vs Levels 29 >
Level 30's should not be match made with or against anything lower than other level 30's.
Smurfing is bad enough to deal with as it is for a new player, but when you get an experienced player on a top level account with all their runes and masteries then not only do they have their 100's of game hours in experience as an advantage over everyone else, but the game mechanics on their side as well!
When queuing for a game as a level 30 you should NEVER wind up in a game with anyone lower than 30 themselves. Sure there is a huge skill difference in someone who has been top level since season 1 and someone who just left 29 that last match, but that's all part of reaching top level yourself, you know what's coming.
I know people will complain about how they want to play with their friends who they just referred, well how about play vs bots for a bit to get them used to the game, and then when you either let them play on their own until they're better, or you can search for a match together and let them know they'll be the only person in that match who isn't top level (Unless someone on the other team also bring their noob friend along too). That's their choice to go into a game where they will most likely get sh*t on, don't force it on anyone who is still learning.
This obviously won't have an effect on smurfing, but that's unavoidable in any free to play game so there is nothing Riot can do. Allowing a team full of players levelled at 19, 20, 20, 21, 21 to go against a team with levels 10, 11, 20, 30, 30, is not balance. Those level 10's are probably only a tiny bit worse than the 21's they're against, those level 30's however could have reached level 30 twenty times over by now.
If I had to make an educated guess, I'd say a measly third of my games have been unaffected by poor matchmaking. Before anyone says I'm just crying about losing, well many of those games I had the top level wind up on my team. Getting hard carried by 1 person is just as dull and frustrating as being completely wiped by 1 person.
Let the Level 30's fight amongst themselves. I'll happily get carried or wiped when I'm at that level myself.